As thickness reduction of a wiring substrates progresses, a wiring substrate that has two or three wiring layers can be formed with a thickness less than 100 μm. Because the rigidity of the substrate of such thin wiring substrate is low, the thin wiring substrate is difficult to handle during a manufacturing process. Therefore, to ensure the rigidity of the substrate, a wiring substrate having multiple wiring members layered on a support member is proposed.
Patent Document 1: Japanese Laid-Open Patent Publication No.: 2013-138115
However, with the conventional wiring substrate having multiple wiring members layered on a support member, the layer structure of the support member is not optimized for a wiring member. Thus, the support member may be thicker than required for the wiring member.